The cutaneous angio dysplasia, one example of which is the skin angioma, better known as the "port-wine stain", results from hypervascularization of the dermis which produces an unaesthetic and unsightly effect on the patient's skin.
At the present time, there are known methods of treating cutaneous angio dysplasias that consist in blocking the blood vessels in the skin area concerned so as to obtain permanent discoloration of the lesion without thereby producing any side effects.
Nowadays, the laser technique is generally used by the practitioner to block the blood vessels manually by photocoagulation with the help of a laser, for example, an Argon-type laser.
In particular, an Argon laser produces radiation that is suitable for the treatment of cutaneous anglo dysplasias as it is well absorbed by the living tissues with a preferential effect on the red and black pigments. That is why the thermal effects of the Argon laser are often used in the treatment of such symptoms.
With specific regard to the treatment of cutaneous angio dysplasias, the desired thermal effects correspond to a temperature of between 60.degree. and 80.degree. C., which has to be confined to the micro-vessels of the dermis to avoid any necrosis of the tissues presenting risks of scar formation.
In general, this method of treatment is carried out manually by the practitioner who, using an Argon laser source equipped with a controlled attenuating shutter for adjusting the irradiation time and an optical fiber to transmit the laser energy generating a laser spot, effects laser shots to produce a plurality of closely grouped impacts on the area to be treated.
In this case, the practitioner's skill is of prime importance as he has to exercise control over all the treatment parameters, namely radiation power, exposure time, the relative positioning of the different impacts and their uniformity.
The success of the treatment thus depends primarily on the practitioner and his skill in controlling these parameters which can determine a wide range of thermal effects, both in terms of the temperature attained which leads either to coagulation or to volatilization, and of the localization of this temperature rise.
Owing to these different parameters that have to be taken into consideration, the present efficiency of such a treatment corresponds to about 50 to 60% of successful results and patients are thus compelled to apply to highly experienced practitioners as success depends essentially thereon.
Moreover, in most cases, cutaneous anglo dysplasias cover large areas, in the order of several square centimeters, which are not always flat surfaces and, as the diameter of the elementary laser spots at the impacts is in the order of one millimeter, the practitioner, when applying the treatment, will be compelled to juxtapose several hundreds of shots manually with practically no positioning references.
Indeed, owing to the technique used, the practitioner is obliged to wear protective goggles and he does not, therefore, have a clear view of the spot that he is positioning. This also makes it difficult to keep the diameter of the spots produced uniform as this depends essentially on the distance between the optical fiber and the area under investigation.
Furthermore, when these methods are used, local anaesthesia is systematically practised to prevent the patient from experiencing the pain inherent in accumulations of heat.
The cumulative effect of these requirements makes this method of treatment difficult and tedious to apply; moreover, the treatment has to be spread out over several sessions, on one hand for the sake of the patient, who has to keep still during treatment, and, on the other hand, for the practitioner, who has to make an effort of sustained concentration.
To minimize the proportion of failures encountered with this treatment and to facilitate the practitioner's work, the use of robotics has already been contemplated to automate the task.
A few years ago, in fact, treatment equipment was presented that was essentially composed of a robot arm ensuring the controlled movement of a hand-piece in which the optical fiber was disposed.
This method has not been further developed to date as its implementation is a delicate matter since it presupposes the detection of three-dimensional shapes and does not make any allowances for the patient's movements during treatment.
While this equipment facilitates the practitioner's work, it gives results that are inferior to those obtained using the traditional manual method.
On the other hand, it is also known to use a hand tool, designed according to the same principle as the above-mentioned device, that is positioned by the practitioner, that is to say with the help of an optical fiber contained in a portable case transmitting the energy of a laser source, but the elementary spot of which has been spread by using an anamorphic optical system.
However, with this instrument, it is difficult to make the spot uniform and, in addition, the depth of field is very small. Furthermore, to observe the treatment parameters mentioned earlier, use is made of a high-power laser source, which is an obstacle to its development as this increases the cost of such a system.
There is also known, in particular from U.S. Pat. No. 4,653,495 an apparatus for treating skin angiomas using the energy emitted by a laser source, as shown in FIG. 1.
This apparatus comprises a laser source 61, suitable for emitting a laser beam 62, which is then directed towards an optical system 64 suitable for positioning the laser beam in front of a plurality of optical fibers grouped together at a laser beam scanning unit 63.
More precisely, laser beam 62 is directed towards a mirror 66 and then focussed by a lens 67, and subsequently transmitted to a horizontal layer of optical fibers 69.
As shown in the figure, the apparatus comprises 17 optical fibers, numbered from 69-1 to 69-17.
One of the optical fibers, 69-1, is suitable for transmitting the laser energy to a "single" hand-piece numbered 70. The other 16 optical fibers, 69-2 to 69-17, form a torus and can be directed to a second "multi" hand-piece numbered 71.
During the treatment, the operator can choose to use either the "single" hand-piece 70 or the "multi" hand-piece 71, depending on the size and shape of the area to be treated.
If he decides to use "single" hand-piece 70, the practitioner will then operate manually in accordance with the method of treatment described earlier. It should be noted that this hand-piece can also be used to measure irradiation power by inserting the end of "single" hand-piece 70 into a power measuring device 72.
If the practitioner does not wish to scan the area for treatment manually using "single" hand-piece 70, he can then choose to use the other "multi" hand-piece 71, which will enable him to treat a larger surface area.
In this connection, as shown, in particular, in FIGS. 2a to 2c, there is known a method of treatment referred to as the "zebrine pattern". Up to the time of the present invention, this method was considered as one of the best as it permitted faster treatment than the manual process.
The "zebrine pattern" technique consists in producing a succession of parallel lines of laser impacts 85 having a diameter "d" and spaced apart by a center to center distance "e".
FIG. 2a shows such lines of impacts numbered 80 and 81 which induce the coagulation of two corresponding strips, 80' and 81' on the area to be treated, as shown in FIG. 2b.
After this treatment, hand-piece 21 is re-positioned and two new lines, 82 and 83, of impacts 85 having a diameter "d", and equally spaced apart by a center to center distance of "e", are produced.
As shown in FIG. 2c, these two new lines, 82,83, induce fresh treated strips 82' and 83', which determines a treated surface 80'-83'.
To make it possible to proceed in this way, the end face 71a of "multi" hand-piece 71 has an arrangement of optical fibers 69-2 to 69-17 such as to form impact lines that are parallel and spaced in relation to one another so as to observe the "zebrine pattern" method.
This being so, in certain cases in which the area for treatment is smaller than working surface 71a, this end 71a will advantageously be provided with a mask 73 and a protective end piece 74.
Such a device makes for genuine progress in relation to the manual method of treatment, but it does have numerous drawbacks inherent, on one hand, in the very design of the apparatus and, on the other hand, in the difficulty of repositioning the "multi" hand-piece, as well as in the substantial contamination of the end of the latter.
As regards the structure of such a known device, it is essential, in the first place, to use a bundle of optical fibers arranged in a torus in accordance with a particular type of cabling, namely by causing the fibers of a layer forming cabling configuration to come to form a toroidal cabling configuration, which has an effect on the dimensioning of "multi" hand-piece 71 and on the flexibility of the system as a whole.
Furthermore, at input 63 to the bundle of optical fibers 69, it is necessary to scan the layer of fibers with the laser beam by positioning the latter opposite each end of the optical fibers and on their longitudinal axis via the device 64,66,67. Major problems arise in connection with the design of such a mechanical positioning device, which has to hair precisely and successively opposite each fibre disposed in the layer. This non-material positioning of the laser beam along the axis of the fibers is an extremely delicate matter.
As to the application of the treatment, it should be noted that considerable difficulties are involved in repositioning the end 71a of the "multi" hand-piece 71 in order to intercalate new lines 82,83 of impacts between the already treated strips 80' and 81', as shown in particular in. FIG. 2b.
This method of working is rendered necessary by the effect of thermal diffusion around the impacts made which causes heat accumulation that has to be taken into account in order to avoid overheating in the area treated.
Similarly, to allow for the Gaussian profile of the laser spot emitted, it is necessary, in certain case, to create overlapping impacts, as also shown in FIG. 2.
Moreover, in order to increase the surface area treated, we have to turn to large diameter fibers. There are thus devised, in U.S. Pat. No. 4,653,495, laser fibres of a polygonal cross-section to permit better coverage of the surface treated; however, these are technically impossible to produce by means of flexible optical fiber manufacturing processes known to date.
This being the case, it is to be noted that the apparatus described in this U.S. patent works in contact with the skin, that is to say the end 71a of "multi" hand-piece 71 has to be placed in direct contact with the area to be treated.
Such a procedure increases the difficulty of repositioning the hand-piece at a subsequent stage and, moreover, leads to contamination of the ends of the optical fibers.
As a result of all these major drawbacks, no apparatus according to U.S. Pat. No. 4,653,495 is yet on the market or in service in medical circles.
This being the case, in a completely different medical field, DAVI, U.S. Pat. No. 4,266,548 discloses a process and a device, using laser energy, for excising pathological tissues. This process consists in vaporizing pathological tissues inside a patient's body.
Such an apparatus is composed of a laser source, a collimator, a flexible optical waveguide linking the laser source to the collimator, a device for deflecting the laser beam inside the collimator, as well as a mechanical device for prepositioning the collimator assembly outside a patient at X, Y, Z.
To operate inside a patient, the collimator ends in a rigid cannula which forms a waveguide and which enables the laser energy to be directed towards the tissue to be vaporized.
To give the laser beam a certain radius of activity within the patient's body, the deflector device, comprising in particular a deflector crystal, subjected to mechanical stresses via electrodes, makes it possible to deflect the laser beam within a range of small amplitude.
In such a case, it is to be noted that we are concerned with an invasive surgical operation to introduce the cannula into the patient's body and it is therefore necessary to preposition the collimator at X,Y,Z outside the patient.
This prepositioning is carried out using a traditional mechanical assembly composed of three motors equipped with endless screws placed on the three axes X,Y,Z, the dimensions of which are very large.
The problem posed by this document, U.S. Pat. No. 4,266,548, is completely different from those inherent in the treatment of skin angiomas and it is in no case possible to transpose this technique to the invention.